The first compositions for shampoo were formulated exclusively for cleaning hair, not for conditioning them. With a view to innovate, providing convenience to the routine of caring for men's and women's hair, one introduced 2-in-1 shampoo, the technology of which has enabled one to introduce ingredients with conditioning properties into conventional shampoo compositions, by using ingredients that promote immediate conditioning by deposition onto the hair fiber, such as quaternized proteins, polyquaternium, silicones, among others. In conventional shampoos, the oily layer protecting the strands of hair is removed with anionic surfactants while cleaning the hair. In 2-in-1 shampoo, the anionic surfactants act cleaning the hair as a function of their detergent power, which captures dirty fragments and, sometimes, the above-cited conditioning ingredients and deposits them on the fiber and condition the strands.
Generally, the conditioning agents have positively charged molecules that neutralize the negative charges of the hair surface and aid in eliminating the repulsion of the strands, reducing frizz.
The great manufacturers of 2-in-1 shampoos usually employ to methods known in the prior art.
The first one, developed and marketed in the late Sixties and used until today, involves mixing cationic polymers with anionic shampoos.
The second method employed in 2-in-1 shampoos uses a micro suspension of silicone in anionic shampoo. The binding between the surfactant and the polymer is water-sensitive and, with the wash, the binding breaks and the surfactant separates from the conditioning polymer. Conditioning polymers, which are insoluble in water, remain on the hair, forming a layer that is deposited onto the strands and conditions them. Although these technologies are commercialized since decades ago, there are great challenges in using them, from both the technical point of view—as, for instance, the difficulty in preventing complexation between the conditioning agents and the surfactants—and the point of view of the consumer, since it is necessary to develop a composition with an appropriate balance of silicones and other conditioning ingredients that provide adequate conditioning, without leaving a residue that, with prolonged use, causes the undesirable effect known as build-up (the feeling of heavy hair due to accumulation of residues on the hair fiber).
With a view to optimize the 2-in-1-shampoo technology, the cosmetic industries have directed their researches to the promising area of nanotechnology. Nanotechnology is an innovative science that includes design, characterization, production and application of structures, devices and systems, controlling shape and size on the nanometric scale, on which 1 nanometer is 1 billionth of a meter. On the nanometric scale, the structures may acquire new properties. It is nothing new for the cosmetic companies that the nanotechnology is the way to the future and is considered the most emergent technology available.
With wide application in various types of cosmetic products, lipidic nanoparticles were considered excellent cosmetic release systems. Lipidic nanoparticles are basically a mixture of lipids and waxes in water, stabilized by surfactants and reduced to submicrometric sizes. These structures have various characteristics that are advantageous, as for example, high biocompatibility, chemical stabilization of actives, controlled release, among others.
The use of nanoparticles in the various industrial sectors evidences the importance of their physicochemical properties, proving to be a field that can grow even more, being highly promising, mainly in the area of cosmetics, which already had a market of 155.8 billion dollar in 2012.
A few examples of prior-art documents related to conditioning shampoos and possibly involving nanotechnology are presented hereinafter.
Patent EP 1465584, published on Jul. 10, 2003, in the name of Rhodia, relates to an aqueous cosmetic composition having a 2-in-1 shampoo. In order to solve the problem related to the combined use of anionic and cationic surfactants in 2-in-1 cosmetic compositions, the composition of said invention uses ammonium quaternaries, such as cetyltrimethyl ammonium chloride and behentrimonium chloride as cationic surfactants, alkyl sulfates as anionic surfactants, besides oily substances such as oils (almond oil and palm oil), waxes and derivatives of silicone, wherein the prior-art problem is solved with improvement of the stability of the composition at a low temperature. In spite of describing a cosmetic composition of the 2-in-1-shampoo type, said document does not deal with nanotechnology, or even the use of lipidic nanoparticles.
On the other hand, patent FR 2,920,983, published on Feb. 26, 2010, in the name of L'Oréal, relates to cosmetic compositions for use on hair in the form of oil-in-water (O/A) nanoemulsion with particle size smaller than 350 nm, comprising a cationic polymer and one or more cationic conditioning agents, which may be a cationic surfactant (cetyltrimethyl ammonium chloride and behentrimonium chloride), containing karité butter and palm oil. Patent EP 1,430,867, published on Feb. 10, 2010, also in the name of L'Oréal, relates to processes for preparing cosmetic compositions as well as to the cosmetic compositions themselves, for use on hair, in the form of nanoemulsion with particle size smaller than 100 nm, comprising cationic surfactants, karité butter, sweet-almond oil and palm oil as well.
Both documents above deal with nanoemulsions, called also mini-emulsions, sub-micron emulsions, ultrafine emulsions, among other names, which are transparent or translucent systems containing droplets on the nanoscale, usually with an average diameter ranging from 10 to 500 nm, depending on the preparation process. The main limitation for the development and application of nanoemulsions relates to the stability thereof. Although it is known that these systems could remain stable for years, Oswald ripening may cause instability in the system, making the use of nanoemulsions difficult. Thus, in many cases, it is necessary to prepare the nanoemulsions shortly before the use thereof. Besides, nanoemulsions generally exhibit lower capability of incorporating actives with respect to lipidic nanoparticles. On the other hand, the present invention comprises lipidic nanoparticles consisting of a lipophilic solid matrix, in which active molecules may be incorporated. The particle size ranges mainly from 150 to 300 nm, wherein sizes smaller than <100 nm or bigger than 1000 nm may be obtained according to the preparation process and depending on the need and objectives. Lipidic nanoparticles may be derived from oil-in-water nanoemulsions, wherein the liquid lipid of the oil droplets is replaced by a solid lipid, that is, solid at body temperature. So, lipidic nanoparticles remain solid after administration to the body. Lipidic nanoparticles act as a matrix, protecting labile/instable and/or incompatible actives. They exhibit excellent physicochemical stability and greater capability to incorporate actives into the matrix, which may function as a controlled-release system.
Further with regard to the prior art, conditioning shampoos existing on the market, which use cationic polymeric conditioning agents, such as quaternized proteins, gums, polyquaternium, silicones, among others, have a few drawbacks. One of them is the technical challenge, since there may be complexation between the cationic agent and the anionic surfactant system, causing destabilization of the formulation.
Besides, compositions containing gums, silicones, quaternized proteins, etc, used in conditioning shampoos found on the market promote an immediate conditioning through mechanism of depositing material onto the hair fiber, by virtue of the molecular weight of these ingredients, but they do not treat the fiber internally. In the long run, they may further cause the undesirable build-up effect due to accumulation of product residues on one's hair.
Thus, one of the main objectives of the present invention is to bring about immediate and long-term conditioning through encapsulation of cationic surfactants, for instance, derived from quaternary ammonium, in lipidic nanoparticles using oils, butters and waxes, for instance, carnauba wax, as structuring agents of the lipidic carrier (lipidic nanoparticles), associating a long-term treatment effect through substantivity and regeneration of the hair fiber, as well as short-term cleansing effect, conditioning, improvement of combability, softness, brightness, decrease in frizz, decrease in volume, looser hair, among others. Since the positive charge of the conditioning system is not in contact with the negative charge of the shampoo base or other preparations for keratinic substrates (such as shampoos, toilet-soaps, conditioners, hydrating masks, leave-on, among other examples), by virtue of the nanoencapsulation process, the technical difficulty of handling the formulations is minimized, and thus the stabilization thereof is guaranteed. Besides, due to the nanometric size, the nanoparticles are expected to have a greater potential of penetration into the substrate (example: hair fiber), treating it internally instead of depositing only onto the outer area, which minimizes the build-up effect already mentioned before.